1. Field of the Invention
The present invention relates to a device and method for stabilizing the structural integrity of box culvert bridges and similar structures and a portable cofferdam device specifically designed for such purpose.
2. Description of the Related Art
Cofferdams have long been used in the construction field as an effective means of accessing submerged areas. Cofferdams may be used to construct piers and bridge supports in lakes and rivers. Small streams or low flow rivers may be dammed on the upstream side or both upstream and downstream sides of a bridge to conduct necessary repairs or new construction.
Box culvert bridges have long been a popular bridge style in the transportation construction arena due to low cost construction and installation. The typical box culvert bridge is constructed with large multiple concrete tubes or xe2x80x9cbox culvertsxe2x80x9d connected in parallel. The length of the box culverts equals the width of the bridge road surface above. These concrete box culverts allow water flow under the bridge road surface by passing through the culvert. A typical box culvert will have two side walls rising perpendicular from the ground surface and a concrete ceiling (supporting the bridge road above the culverts), and a concrete bottom or floor which rests on the river or stream bottom. Since the typical box culvert bridge design does not require subsurface pier support or piling support, the stability of the riverbed immediately below the culvert bottom is crucial for maintaining the long term structural integrity of box culvert bridges.
Although box culvert bridges are cost effective with regard to construction and installation, riverbed scouring beneath the box culvert bottom can make long term maintenance of such bridges problematic. Specifically, natural changes in hydrologic flow conditions and extra ordinary weather events will destabilize portions of the river bottom and sides adjacent to the culvert bridge jeopardizing the structural integrity of the structure. The typical remedy employed by transportation officials for restoring the subsurface integrity of compromised box culvert bridges is to dam the upstream portion (and, if necessary, the downstream portion) of the river or stream for a period of days or weeks until a work area around the scoured area of the riverbed can be isolated and workers can pump grout or a similar hard curing material under the bridge into the water filled void created by the aforementioned scouring action. The grout or similar hard curing material is typically pumped into the water filled void through a drill hole made into the culvert bottom just above the void.
In recent years, the Federal Highway Administration has adopted more rigorous methods of inspection of such culvert bridges by employing the use of regularly scheduled underwater inspections conducted by experienced scuba divers. These divers can inspect areas under a culvert bridge that have been problematic to inspect in the past. The resulting increased number of inspections has resulted in a larger than expected number of culvert bridge repair needs. Accordingly, the traditional repair methods employed by state and regional transportation departments has failed to effectively address the number of required repairs. The present invention and associated method result in an equally effective but inexpensive means of restoring the structural integrity of culvert box bridges. The present invention does not require the complete damming of a river or stream, saving time, materials and minimizing disturbance to the environment. By employing the use of a portable coffer dam, the subsurface of a culvert bridge can be repaired quickly and cheaply, while also extending the life of the bridge.
It is therefore an objective of this invention to provide a cost effective and efficient method for repairing riverbed scouring below culvert box bridges.
It is further an objective of this invention to provide a facile device of novel design and construction to be used in the subsurface stabilization of culvert box bridges.
It is still further an objective of this invention to provide a environmentally responsible and less intrusive means for improving the long-term maintenance of box culvert bridges and similar bridge designs.
These as well as other objectives are accomplished by a chamber structure small enough to fit inside the culvert of a box culvert bridge, but large enough to house one or more persons and equipment necessary to dewater the chamber structure and pump grout or similar hard curing material through a drill hole in the culvert bottom.
The present invention is employed after identifying riverbed scouring that has occurred beneath the floor bottom of the box culvert bridge. The components of the present invention can be sufficiently compact to be transported in a medium size truck bed to the bridge location. The various components of the device include the aforementioned open chamber structure equipped with an upper expansion device, fluid discharge conduit, quick release hose and pipe connectors, a discharge pump and associated hose conduit. After arriving at the location of the box culvert bridge where the riverbed below the culvert bottom requires subsurface stabilization due to hydrologic scouring, the open chamber is slowly lowered into the river or stream along side the bridge. The water level in the river or creek must not exceed the height of the top portion of the portable cofferdam, as it could not be dewatered. After positioning the open chamber in place and securing the open chamber in place, the upper expansion device is employed to compress the chamber floor seal against the culvert bottom. Afterwards the pump intake conduit can be connected to the chamber intake conduit, and the open chamber is dewatered. The planned bridge repair is conducted by drilling a hole through the culvert bottom within the open chamber above the scour void. Grout or a similar hard curing material is pumped through the drill hole until the scour void is adequately filled. After completing the repair, the chamber upper expansion device can be released or loosened to allow the retrieval of the open chamber from the culvert.
Other aspects, features and other embodiments of the invention will be more fully apparent from the ensuing disclosure.